To Users of the EF40mm f/2.8 STM Interchangeable Lens for Canon Digital SLR CamerasThank you for using Canon products.

It has been confirmed that the autofocusing function of the EF40mm f/2.8 STM lens, which was released in June 2012, may not operate correctly.

The details of this phenomenon are described below.

Affected ProductEF40mm f/2.8 STM

PhenomenonIf pressure is applied to the lens barrel while the lens is mounted to the camera (pressure can be applied even while attaching the lens cap or while carrying the camera with the lens attached in a bag), the autofocusing function of the lens may stop working.

*This phenomenon does not occur during normal shooting.

*This phenomenon does not result in a malfunction of the lens.

WorkaroundWhen the above phenomenon occurs, detach and reattach the lens, or remove and reinsert the camera battery to restore the operations.

Market SupportThe firmware to address this phenomenon will be available for download in late August, 2012.

Once this firmware is ready, we will make an announcement on our Web site.

So...putting your lens cap on might cause it to not be able to AF without taking the lens off and on?

Yeah, that's something that shouldn't have made it past QC testing.

True. It's happened to me putting the lens cap back on. It's not hard to get in the practice of retracting the lens first, though. And you don't have to remove the lens just rotate it a bit and re lock it.

At this price I would think Canon would move heaven and earth to make it a field-upgrade via the body firmware. Factory re-work and reshipment of the thousands of those $199 lenses out there now would nuke their profits.

Of course that means new firmware for all the EF bodies, no? Which means the potential of magic lantern as well I'd think. (Evil cackle)

At this price I would think Canon would move heaven and earth to make it a field-upgrade via the body firmware. Factory re-work and reshipment of the thousands of those $199 lenses out there now would nuke their profits.

Of course that means new firmware for all the EF bodies, no? Which means the potential of magic lantern as well I'd think. (Evil cackle)

I do like the lens although I still hate focus-by-wire.

I am pretty sure they would update ML too to cater for the new firmware. Although I never understood why people are so crazy about the shorty 40 ... Canon DSLRs are big even with a small lens...